 /* 按钮边框的大小、位置、样式 */
 .toTop-arrow {
    width: 3.5rem;
    height: 3.5rem;
    padding: 0;
    margin: 0;
    border: 0;
    border-radius: 33%;
    opacity: 0.7;
    background: black;
    cursor: pointer;
    position: fixed;
    right: 1.5rem;
    bottom: 1.5rem;
    display: none;
}

/* 绘制按钮中的向上箭头 */
.toTop-arrow::before,
.toTop-arrow::after {
    width: 31px;
    height: 7px;
    border-radius: 3px;
    background: orange;
    position: absolute;
    content: "";
}

.toTop-arrow::before {
    transform: rotate(-45deg) translate(0, -50%);
    left: 0.4rem;
}

.toTop-arrow::after {
    transform: rotate(45deg) translate(0, -50%);
    right: 0.4rem;
}

/* 取消点击按钮时的聚焦 */
.toTop-arrow:focus {
    outline: none;
}

